Multi-unit pneumatic control system

ABSTRACT

A pneumatic unit ventilator control system utilizing a diaphragm logic memory circuit for winter-summer changing over to allow the running of a single main from the pressure source to the units. Depending upon the magnitude of the main pressure input to the memory circuit, and upon previous alterations of the main pressure, either summer or winter control will be achieved. Recycling means are included in the system to assure the return of the system to the desired mode of operation after a fluid pressure failure or a changeover from one mode of operation to another.

United States Patent [151 3,672,567

Joesting 1 June 27, 1972 s41 MULTI-UNIT PNEUMATIC CONTROL 3,373,935 3/1968 Thorburn ..236/46 x SYSTEM 3,556,399 1/1971 Puster ..236/47 [72] inventor: Frederick D. Joesting, Park Ridge, Ill. primary Examine, Edwal-d J. Michael [73] Assignee: Honeywell Inc., Minneapolis, Minn. Attorney-Lamont Koontz [22] Filed: Oct. 19, 1970 [57] ABSTRACT [2]] Appl- N -I 82,034 A pneumatic unit ventilator control system utilizing a v diaphragm logic memory circuit for winter-summer changing over to allow the running of a single main from the pressure 'g g source to the units. Depending upon the magnitude of the main pressure input to the memory circuit, and upon previous [58] Field of Search ..236/l C, 46, 47 alterations of the main pressure, either Summer or winter trol will be achieved. Recycling means are included in the [56] References Cmd s stem to assure the return of the s stem to the desired mode Y Y UNlTED STATES PATENTS of operation after a fluid pressure failure or a changeover from 1 one mode of operation to another. 3,047,233 7/1962 Scharpt ..236/l C 3,140,047 7/1964 Holloway ..236/l C v 17 Claims, 10 Drawing Figures TO uu ITS P- E 6-]8 PSI 4 3O COMPRESSOR -43 5s E-P 8 PSI L I 3| 37 7 x 5| 55 5e PSI *g Rv V l3 PSI 2| PSI l2- 25 PSI 25 PSI v i r 42 P3RV g N l PATENTEDJuIm I972 SHEEI 1 OF 4 I0 Io F/G CENTRAL I! l CONTROLLER +wINTER PRESSURE RANGE- FIG 2 WINTER WARM .WINTER DAY P NIGHT P I I o 8 l3 l6 2| 25 MM" F PRESSURE SUMMER SUMMER (PSI) DAY NIGHT .--suMIIIIER PRESSURE RANGE F "I F "3 I75 3 Z 73 o o I I W l MAIN i -lvwvi -l- 74 PM I I Q Q I I O I i "I w i I I i X L: J I MC I. FIG. .9 J I x INVENTOR.

FREDERICK 0. JOESTING A TTORNEX P'A'TENTEDJum 1972 3. 672.567

sum 3 or 4 COMPRESSOR 8 PSI PRV l6 PSI PRV COMPRESSOR INVENTOR: FREDERICK D. JOESTM/G Y: B zrm /vsr This invention relates to multi-unit pneumatic controls particularly for unit ventilator or central fan systems.

Unit ventilator and central fan systems, often used in school buildings and the like, often have two modes of operation; heating and cooling, or winter and summer. Within each mode there may be a number of functions. For example in the summer mode there may be both day and night functions.

During the day a valve or the like may control the flow of a cooling medium, an outdoor air damper may be opened to some minimum position and a fan may run continuously. During the night the valve and damper may be closed and the fan shut off. In the winter mode there may be day and night functions as well as a morning warm-up function. During the day a valve or step controller may control the flow of some heating means, a predetermined ventilation cycle may be in operation, the fan may run continuously and a low temperature limiting means may be included in the circuit. During the night the valve may be held open, the fresh air damper held closed, there may be included a low limit in the circuit, and the fan may cycle on and off to maintain a lowered nighttime temperature. The morning warm-up function would generally be the same as the night function except the unit would be adjusted to maintain the daytime temperature. There may also be included temporary nighttime occupancy or manual reset functions. Hence there may be five or more functions to be performed within the two modes of operation.

It has been customary to perform these various functions by adjusting the main pressure to different values to thereby actuate different controls. In the past it has generally been necessary to run separate main pressure conduits to each unit ventilator or the like in order to perform each of the above described functions. One such conduit is pressurized continuously at selected pressures while the other is pressurized only in one or the other mode in order to actuate or deactuate certain controls. The subject invention allows the running of only a single main pressure conduit to each unit by virtue of a memory circuit which is included in the control circuitry of each unit. The memory circuit takes the place of the previously used second main pressure conduit by either blocking or transmitting the main pressure which is connected thereto. Whether the memory circuit blocks or transmits the main pressure depends upon the magnitude of the main pressure and upon the previous alterations of the main pressure.

The use of the memory circuits gives rise to the possibility that the wrong mode of operation will be effected after an attempted changeover from one mode to the other or after a fluid pressure failure resulting from a leak in the system or from a power failure. A novel electric-pneumatic circuit for altering the main pressure to insure the proper mode of operation is accordingly disclosed and forms an important part of the subject invention.

DESCRIPTION OF THE DRAWING FIG. 1 is a schematic of one type of pneumatic control system utilizing the subject invention.

FIG. 2 is a diagram showing the winter and summer pressure ranges as well as the pressures at which the various functions may be performed.

FIG. 3 is a schematic of an electric-pneumatic circuit for providing the various main pressures required for the various functions as well as recycling means for insuring the proper mode of operation.

FIG. 4 is a table showing the positions of the switches in FIG. 3 required to establish the necessary main pressure to perform a predetermined function.

FIG. 5 is a simplified version of FIG. 3 showing the circuit FIG. 8 is a table showing the valve positions required in the control circuit-of FIG. 7 in order to effect the various modes and functions.

FIG. 9 is an alternative embodiment of the memory circuit included in the illustration of FIG. 7.

FIG. 10 is a second alternative embodiment of the memory circuit.

DETAILED DESCRIPTION OF THE INVENTION While the subject invention will be described within the context of a unit ventilator control system and with reference to specific pressures and pressure ranges, it is to be understood that the scope of the invention is not to be limited by such exemplary pressures and terminology.

FIG. 1 discloses a plurality of unit ventilators 10 connected via a main pressure conduit 11 to a central controller 12. The functions and details of the central controller and of the control circuitry of'the unit ventilators are more fully disclosed in FIGS. 3 and 7 respectively, and will be described below.

In FIG. 7 is a memory circuit 60 comprising three diaphragm valves 61, 62 and 63. Each valve is comprised of a housing divided by a diaphragm into a control chamber 81 and a flow chamber 82. Disposed within the flow chamber is an annular partition 83 which, with the diaphragm 80, defines a valving chamber 84. Within each control chamber is a spring 85 arranged to urge the diaphragm downwardly to close-off the valving chamber 84. A spring illustrated as having a single diagonal coil denotes the presence of a light closing spring. Such a spring is designed to exert a force equivalent of about 1 psi or less and is included to insure that the valve is closed if the pressures in the control and flow chambers are equal. A spring illustrated as having two vertical columns of coils denotes the presence of a somewhat heavier closing spring. The function of each such heavier spring will be described below.

The main pressure conduit 11 is connected to the valving chamber of valve 61 and to the flow chamber of valve 62. The closing spring or biasing spring in valve 61 is designed to exert a force on the diaphragm sufficient to hold the valve closed until a pressure of approximately 20 psi is reached in the valving chamber. Of course another biasing means other than the spring could be used such as a regulated supply of air pressure. If valve 61 is initially closed, the control chamber of valve 62 will not be pressurized so the main pressure will cause valve 62 to open and the main pressure will be therefore transmitted via the memory circuit outlet designated MC to inlets of the control chambers of valves 66 and 67 likewise designated MC. The closing spring in valve 63 is designed to exert a force sufficient to hold the valve closed until a pressure of approximately 12 psi is reached in the flow chamber. Hence if the main pressure is in excess of l2 psi but does not exceed 20 psi so that valve 61 reamins closed, the main pressure will also be transmitted via the memory circuit outlet designated X to the inlets of the control chambers of valves 64, 65 and 71.

If at any time the main pressure exceeds 20 psi, valve 61 will open allowing the pressurization of the control chamber of valve 62 and thereby closing of valve 62. The pressure in the valving chamber of valve 62 thereafter bleeds to atmosphere through restriction 86 and the output pressure or pressures MC and X of the memory circuit drop to 0.

The diameter of the annular partition 83 of valve 61 is designed to provide the valve 61 with a wide differential of approximately 10 psi. This differential is achieved by virtue of the greater surface area of the diaphragm over which the pressure in the flow chamber 82 may act when the valve is open as opposed to the somewhat lesser surface area over which the pressure in the valving chamber 84 may act when the valve is closed. By reason of this wide differential the valve 61 will remain open if the main pressure falls below 20 psi even though 20 psi was required to open the valve. If, however, the main pressure falls below 10 psi, the valve 61 will close and will remained closed until the main pressure again exceeds 20 psi. This permits valve 62 to open and establishes main pressure at MC. If the main pressure exceeds 12 psi while valve 61 is closed, main pressure is established at both MC and X. If the main pressure remains below l2 psi, the X output will remain 0. Hence, depending upon the magnitude of the main pressure and upon the previous alterations of the main pressure, the output or outputs of the memory circuit will either be or equal to the main pressure. The MC and X outputs of the memory circuit being zero establishes a winter mode of operation, whereas the summer mode of operation is effected if main pressure exists at MC and either 0 or main pressure exists at X. How the memory circuit output establishes one or the other modes of operation will be described below.

FIG. 9 is a schematic of an alternative embodiment of the memory circuit 60. The memory circuit of FIG. 9 is the same as the memory circuit 60 except that the main pressure conduit is connected to the flow chamber of the wide differential valve instead of the valving chamber. As in the case of memory circuit 60, the diameter of the annular partition forming the valving chamber of valve 75 must be such that the desired opening and closing pressures of the wide differential valve are obtained. The valves 75 and 76 in FIG. 9 operate in the same manner as valves 62 and 63 in memory circuit 60. The pair of valves 75 and 76 can be considered a diaphragm logic element, similar to elements 100, 101 and 102, to be described below.-

FIG. 10 is a second alternative embodiment of the memory circuit 60. In FIG. 10 the two valve means 73 and 74 comprise the wide differential valve means. The closing spring of valve means 73 provides the psi opening point of the wide differential valve means and the closing spring of valve means 74 provides the 10 psi closing point. The use of two valves obviates the use of a valve having a wide diameter annular panition. In addition, if the forces exerted by the springs in valves 73 and 74 are made adjustable, the opening and closing points of the wide differential valve means may be independently adjusted. The valves 73 and 74 provide a wide differential valve means in the following manner: as the main pressure increases from O to 20 psi, both valves 73 and 74 are held closed by their respective springs; when the main pressure exceeds 20 psi, valve 73 opens and thereafter transmits pressure to the flow chamber of valve 74 whereupon valve 74 opens; when the main pressure falls below 20 psi, valve 73 closes but valve 74 remains open until the main pressure in its flow chamber falls below 10 psi. Thus valves 73 and 74 provide the same wide differential valve function as do valves 61 and 75. The other two valves in FIG. 10 functions in a way similar to valves 62 and 63 in memory circuit 60.

As shown in FIG. 2 the summer operational mode or first operational mode corresponds to a pressure range of approximately 0 to 20 psi while the winter operational mode or second operational mode corresponds to a pressure range of approximately l0 to psi. As illustrated and earlier explained the valve 61 remains closed as the pressure increases from 0 to approximately 20 psi. At that point it opens upon a further increase in pressure and remains open until the pressure falls below approximately 10 psi. Hence depending upon whether the pressure rises into or falls into the range of pressure between 10 and 20 psi, the mode of operation in that pressure range of [0 to 20 psi may be either summer or winter. The functions associated with the summer mode of operation in-clude summer-day, corresponding to 8 psi, and summernight, corresponding to 16 psi. The functions associated with the winter mode of operation include winter-day, corresponding to 13 psi, morning warm-up, corresponding to 16 psi, and winter-night, corresponding to 21 psi.

The central controller 12 in FIG. 1 is schematically illustrated in detail in FIG. 3. A source of air pressure such as a compressor is connected to a plurality of pressure reducing valves 31-35 (PRVs) or pressure regulating means. Connected to each of the PRV's are electric-to-pressure (E-P) relays 3640. Each of the 13-1 relays is normally closed so that fluid will be allowed to pass therethrough only when the relay is electrically energized. Each of the relays is connected to the main pressure conduit 11. Note that the main pressure will be the output of the PRV having the highest setting which is connected to the main pressure conduit. It is not necessary to close-off the PRVs having lower pressure pressure settings. Which of the 13-? relays is energized and therefore which pressure output is transmitted to the unit ventilators depends upon which of the switches 51-58 are closed. As shown in the table of FIG. 4, switches 51 through 55 provide for the changing over from winter to summer or from summer to winter. Switch 56 establishes either the summer-day or summer-night function while switches 57 and 58 establish the winter-day, winter- I night and the winter warm-up functions. These switches may be either manually closed or may be operated by a time clock or the like. The recycling function which insures the proper mode of operation after a changeover from one mode of operation to another or after a pressure failure is provided by PRV 35, E4 relay 40, electric relay 41, and pressure-to-elec tric (P-E) switches 42 and 43. P-E switch 42 closes at approximately 12 psi and opens at approximately 25 psi. P-E switch 43 closes and opens at approximately 6 psi and 18 psi respectively. The operation of this recycling means is best understood by example.

FIG. 5 shows the circuit of FIG. 3 in a simplified form for summer operation. Only the components which function in the summer mode of operation are shown. P-E switch 43 will be closed during the summer operation since the highest pressure corresponding to a summer function, 16 psi, is less than the switch point of 18 psi for P-E switch 43 and, as will be explained below, P-E switch 43 has been cycled below 6 psi in order that it be closed. If there is a pressure failure due to a pressure leak or a power failure for example, switch 43 will remain closed so that upon resumption of pressure, the summer mode of operation will continue. On the other hand during winter operation P-E switch 43 will always be open since the pressure will have been cycled above 18 psi. Accordingly when the system is switched from winter to summer operation, the pressure in the main pressure conduit will immediately begin to fall since none of the E-P relays will be energized. When the pressure in the main pressure conduit falls below 6 psi, switch 43 will close and normal summer operation will commence. The closing point or pressure of switch 43 is not critical, but the pressure should be somewhat less than the switching point of valve 61 in the memory circuit, which is 10 psi, in order to insure that the most remote valves are switched closed.

Referring to FIG. 6, P-E switch 42 will normally be opened during winter operation. If however, a pressure failure occurs and the pressure falls below 12 psi giving rise to the danger of switching to summer operation, switch 42 will close. When power resumes relay 41 will immediately energize and therefore open E-P relay 40. 25 psi will then be established in the main pressure conduit until 25 psi is attained at switch 42. This recycling of the pressure to 25 psi after a failure assures that each of the valves 61 in the memory circuits in the individual unit ventilators have fully opened and that therefore each of the unit ventilators will return to winter operation. When the system is switched from summer to winter operation, since P-E switch 42 will be closed during summer operation, relay 41 will immediately be energized upon the switch over and 25 psi will be established in the main pressure conduit until P-E switch 42 is opened. Thereafter normal winter operation will commence. As in the case of switch 43 the opening pressure point of 25 psi for switch 42 is selected because it is in excess of the switching points of valves 61 in the memory circuits. This excessive pressure is desirable to be sure that each of the valves 61 in all of the remote units will be opened. Thus it is appreciated that irrespective of when the system is changed from one mode of operation to another, or when there occurs a pressure failure, the proper mode of operation will always be achieved. Thus far the operation of the memory circuit has been explained as well as the purpose and function of the recycling means. An analysis of FIG. 7 will reveal exactly how the central controller, which provides the various main pressures, the memory circuit, which provides certain outputs in response to the main pressure, and the control circuitry at the unit ventilator cooperate to provide the several modes of operation in multiple functions.

The unit ventilator control circuitry or pneumatic programming apparatus has essentially one input, the main pressure, and three output signals for controlling a fresh air damper and perhaps a bypass damper, a heating and/or cooling valve, and a P-E switch controls a fan. The P-E switch closes and the fan goes on when the pressure transmitted to the P-E switch reaches about 2 psi and the switch opens and the fan goes off when the pressure reaches about 4 psi. The main pressure conduit 11 is connected to a pneumatic thermostat 90, memory circuit 60, to means 91, and to the relay 92 via valve 64. The branch line 93 from the thermostat is also connected to means 91 as well as to relay 92 and valve 94 via valves 66 and and 70 and to the P-E switch 95 via valves 66 and 72. The relay 92 is of the type which provides a pneumatic ventilation cycle such as is disclosed in U.S. Pat. No. 3,605,781.

Means 91 comprises apparatus for selectively providing a branch line pressure output or an inverted branch line pressure output. Two parallel paths are provided for the branch line pressure; through restriction 96 and valve 66, or through valve 65, inverter 97 and valves 68. The low limit 98 connected to the first path or inverter by-pass means provides a bleed to atmosphere if the temperature falls below some predetermined level. The resulting decrease in the branch line pressure down stream of the low limit causes the fresh air damper to go to a minimum position and the normally open valve 94 to open whereby the flow of some heating medium is increased. The inverter 97 in the second path is of the type disclosed in applicants co-pending application, Ser. No. 66,714, filed Aug. 25, 1970.

Valves 67 and 68 comprise a diaphragm logic element 100 similar to an electrical relay. Valve 67 has two inputs; a main pressure input to the flow chamber 82 and a memory circuit MC input to the control chamber 81. If the memory circuit output is 0 as is the case in the winter mode of operation, the main pressure will cause valve 67 to open. The control chamber of valve 68 will therefore be pressurized and valve 68 will be closed. The inverter output will accordingly be blocked and the output of means 91 will be the branch line pressure. On the other hand if there is a memory circuit output as is the case in summer operation, valve 67 will be forced closed, allowing the pressure in the control chamber of valve 68 to bleed through restriction 99. Any output pressure of the inverter in excess of the force exerted by the light closing spring in valve 68 will cause valve 68 to open. Since the memory circuit output also causes valve 66 to be closed so that the inverter by-pass means is blocked, the output of means 91 will now be inverted branch line pressure as is desired in summer operation. The function of valve 65 in means 91 will be described below.

Valves 69 and 70 comprise a diaphragm logic element 101 similar to logic element 100. One input to valve 69 comprises a heavy closing spring 103 disposed within the control chamber and designed to exert a force equivalent to approximately 14 psi. The other input to valve 69 is the main line pressure downstream of valve 64. If the main pressure input exceeds 14 psi, valve 69 will open, causing the closing of valve 70 and thereby the blocking of the communication of the output pressure of means 91 to valve 71, relay 92, and valve 94.

Valves 7] and 72 comprise a diaphragm logic element 102 similar to logic elements 100 and 101. The two inputs to valve 71 are the X output pressure of the memory circuit connected to the control chamber, and the output of means 91, provided that the output is not blocked by valve 70. Again depending upon the relative magnitudes of the two input pressures to valve 71, valve 72 will either be open or closed.

As noted earlier the memory circuit provides an output or outputs only during the summer. During the summer-day function the memory circuit output will be main pressure or 8 psi and the X output of the memory circuit will be 0. During the summer-night function however both the MC output arid the X output of the memory circuit will be main pressure, or 16 psi. Hence during the summer-night function the X output will cause valves 64, 65 and 71 to close. The closing of valve 64 will render relay 92 inoperative so that the vent or fresh air damper will be closed. The closing of valve 65 will effectively cause the branch line pressure to the inverter 97 to be 0. The output of the inverter or of means 91 will be the inverse of a zero branch line pressure, or roughly main line pressure, which pressure will be transmitted to the valve 94 to hold valve 94 closed. The closing of valve 71 by the X output pressure of the memory circuit will result in the opening of valve 72 so that the output of means 91 will also be transmitted to the P-E switch which will cause the fan to be shut off. A summary of the valve positions for the summer night function appear in the table of FIG. 8.

A second example of the operation of the control circuitry or programmer apparatus of the unit ventilator will be explained for the winter-day function.

The operation of the recycling means when switching to winter-day will cause valve 61 to be open so that the memory circuit outputs will both be 0. Accordingly valve 67 will be open and valve 68 closed, blocking the output of the inverter. Hence the output of means 91 will be branch line pressure. Because the main pressure during winter-day of l3 psi is less than the 14 psi bias in valve 69, valve 69 will remain closed so that valve 70 will be open. The branch line pressure output of means 91 will accordingly be transmitted to relay 92 and valve 94. The damper position and the position of valve 94 will change in response to changes in the thermostatic output pressure or branch line pressure. Again since the output of the memory circuit is zero, valve 71 will be open and accordingly valve 72 will be closed. Since no pressure is thereby transmitted to the P-E switch 95, the fan will run continuously. While the operation of the programmer apparatus of the unit ventilator for the remaining functions will not be described, the operation may easily be deduced from the table of FIG. 8.

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. In a multi-unit pneumatic control system having a plurality of operational modes and means providing a predetermined pressure range corresponding to each mode, a plurality of functions performable within each mode and means providing a predetermined pressure corresponding to each function, a main pressuresource, a main pressure conduit interconnecting the source and each of the units, and means to establish in the main pressure conduit each predetermined pressure corresponding to each function;

memory circuit means associated with each unit and con nected to the main pressure conduit providing a first output when the system is in a first operational mode and providing a second output when the system is in a second operational mode, the pressure ranges associated with the first and second operational modes substantially overlapping; and

means to recycle the main pressure transmitted to the units after a fluid pressure failure or a changeover from one mode of operation to another whereby the memory circuit functions to provide an output corresponding to the desired operational mode.

2. The control system according to claim 1 wherein;

the first operational mode corresponds to summer operation of the system; and

the second operational mode corresponds to winter operation of the system.

3. The control system according to claim 2 wherein the first output of the memory circuit is main pressure and the second output of the memory circuit is substantially zero.

4. The control system according to claim 2 wherein;

the functions within the first operational mode include summer-day operation and summer-night operation; and,

the functions within the second operational mode include winter-day operation, winter-night operation and morning warmiup operation. 5. The control system according to claim 4 wherein the first output provided by the memory circuit is main pressure, the second output provided by the memory circuit is zero, and the memory circuit additionally provides a third output equal to themain pressure during the summer-night function.

6. The control system according to claim 1 wherein the memory circuit includes first and second valve means connected to the main pressure conduit, the first valve means having a wide differential and arranged to close the second valve means when the main pressure reaches a first predetermined level and to open the second valve means when the main pressure reaches a second predetermined level, the first level being higher than the second level, the output of the second valve means comprising the first and second outputs of the memory circuit.

7. The control system according to claim 6 wherein the memory circuit additionally comprises third valve means connected to the second valve means, the output of the third valve means providing a third memory circuit output, the first and third outputs of the memory circuit being main pressure and the second output being 0.

8. The control system according to claim 6 wherein the recycling means comprises:

pressure regulating means connected to the main pressure source and arranged to provide a pressure sufficient to open the wide differential valve means;

electric-to-pressure relay means connected to the pressure regulating means;

means to establish a circuit to energize the electric-to-pres sure relay means to allow the transmission of pressure to each of the units after a fluid pressure failure while the system is in winter operation or when the system is switched from summer operation to winter operation; and,

means to prevent the transmission of pressure from the main pressure source to the units after the system is switched from winter operation to summer operation to allow the pressure in the main pressure conduit to sufficiently decrease whereby the closing of the wide differential valve means is assured.

9. The control system according to claim 8 wherein means to establish a circuit includes:

first pressure-to-electric switch means arranged to close when the pressure in the main pressure conduit falls below a predetermined minimum level and to open when the pressure exceeds a predetermined maximum level; and,

electric relay means arranged to establish a circuit to energize the electric-to-pressure relay means when the pressure-to-electric switch means is closed.

10. The control system according to claim 9 wherein the means to prevent the transmission of pressure from the main pressure source to the units includes second pressure-to-electric switch means arranged to close when the pressure in the main pressure conduit falls below a predetermined minimum level and to open when the pressure exceeds a predetermined maximum level, the opening of the second pressure-to-electric switch means rendering inoperable said means to establish in the main pressure conduit each predetermined pressure corresponding to each function. 1

11. In pneumatic programming apparatus including a main line pressure input, condition responsive means connected to the main line pressure input and providing a branch line pressure output, a first outlet, a second outlet and a third outlet:

relay means connected to the main line pressure input and the branch line pressure output, the relay means having an output connected to the first outlet; first means connected to the branch line pressure output and the main line pressure input to selectively provide a branch line pressure output or an inverted branch line pressure output, the outlet of the first means connected to said second and third outlets; second means to selectively block the communication of pressure between the first means and the second outlet;

and,

third means to selectively block the communication of pressure between the first means and the third outlet.

12. The pneumatic programming apparatus according to claim 11 wherein the first means includes inverter means having a branch line pressure input, a main line pressure input and an outlet, inverter by-pass means connected in parallel with the inverter means, first valve means to selectively block the branch line pressure input to the inverter means, second valve means to selectively block the outlet of the inverter means, and third valve means to selectively block the inverter by-pass means.

13. The pneumatic programming apparatus according to claim 12 wherein the second valve means of the first means, the second means and the third means each comprises diaphragm valve means having an inlet, an outlet, and first and second inputs, communication of pressure being allowed between the inlet and outlet when the first input is greater than the second output, and communication of pressure not being allowed between the inlet and the outlet when the second input is greater than the first input.

14. The pneumatic programming apparatus according to claim 13 further comprising fourth valve means connected between the main line pressure input and the relay means to selectively block the communication of pressure between the main line pressure input and the relay means.

15. The pneumatic programming apparatus according to claim 14 wherein the first, third, and fourth valve means each has an inlet, an outlet, and an input.

16. The pneumatic programming apparatus according to claim 15 further comprising memory circuit means connected to the main line pressure input and having first and second outputs, the first output connected to the first input of the second valve means and the input of the third valve means, and the second output connected to the inputs of the first and fourth valve means and to the first input of the second valve means.

17. The pneumatic programming apparatus according to claim 16 wherein the second input of the second valve means is connected to the main line pressure input, the second input of the second means is connected to the outlet of the fourth valve means, and the second input of the third means is connected to the outlet of the second means. 

1. In a multi-unit pneumatic control system having a plurality of operational modes and means providing a predetermined pressure range corresponding to each mode, a plurality of functions performable within each mode and means providing a predetermined pressure corresponding to each function, a main pressure source, a main pressure conduit interconnecting the source and each of the units, and means to establish in the main pressure conduit each predetermined pressure corresponding to each function; memory circuit means associated with each unit and connected to the main pressure conduit providing a first output when the system is in a first operational mode and providing a second output when the system is in a second operational mode, the pressure ranges associated with the first and second operational modes substantially overlapping; and means to recycle the main pressure transmitted to the units after a fluid pressure failure or a changeover from one mode of operation to another whereby the memory circuit functions to provide an output corresponding to the desired operational mode.
 2. The control system according to claim 1 wherein; the first operational mode corresponds to summer operation of the system; and the second operational mode corresponds to winter operation of the system.
 3. The control system according to claim 2 wherein the first output of the memory circuit is main pressure and the second output of the memory circuit is substantially zero.
 4. The control system according to claim 2 wherein; the functions within the first operational mode include summer-day operation and summer-night operation; and, the functions within the second operational mode include winter-day operation, winter-night operation and morning-warm-up operation.
 5. The control system according to claim 4 wherein the first output provided by the memory circuit is main pressure, the second output provided by the memory circuit is zero, and the memory circuit additionally provides a third output equal to the main pressure during the summer-night function.
 6. The control system according to claim 1 wherein the memory circuit includes first and second valve means connected to the main pressure conduit, the first valve means having a wide differential and arranged to close the second valve means when the main pressure reaches a first predetermined level and to open the second valve means when the main pressure reaches a second predetermined level, the first level being higher than the second level, the output of the second valve means comprising the first and second outputs of the memory circuit.
 7. The control system according to claim 6 wherein the memory circuit additionally comprises third valve means connected to the second valve means, the output of the third valve means providing a third memory circuit output, the first and thirD outputs of the memory circuit being main pressure and the second output being
 0. 8. The control system according to claim 6 wherein the recycling means comprises: pressure regulating means connected to the main pressure source and arranged to provide a pressure sufficient to open the wide differential valve means; electric-to-pressure relay means connected to the pressure regulating means; means to establish a circuit to energize the electric-to-pressure relay means to allow the transmission of pressure to each of the units after a fluid pressure failure while the system is in winter operation or when the system is switched from summer operation to winter operation; and, means to prevent the transmission of pressure from the main pressure source to the units after the system is switched from winter operation to summer operation to allow the pressure in the main pressure conduit to sufficiently decrease whereby the closing of the wide differential valve means is assured.
 9. The control system according to claim 8 wherein means to establish a circuit includes: first pressure-to-electric switch means arranged to close when the pressure in the main pressure conduit falls below a predetermined minimum level and to open when the pressure exceeds a predetermined maximum level; and, electric relay means arranged to establish a circuit to energize the electric-to-pressure relay means when the pressure-to-electric switch means is closed.
 10. The control system according to claim 9 wherein the means to prevent the transmission of pressure from the main pressure source to the units includes second pressure-to-electric switch means arranged to close when the pressure in the main pressure conduit falls below a predetermined minimum level and to open when the pressure exceeds a predetermined maximum level, the opening of the second pressure-to-electric switch means rendering inoperable said means to establish in the main pressure conduit each predetermined pressure corresponding to each function.
 11. In pneumatic programming apparatus including a main line pressure input, condition responsive means connected to the main line pressure input and providing a branch line pressure output, a first outlet, a second outlet and a third outlet: relay means connected to the main line pressure input and the branch line pressure output, the relay means having an output connected to the first outlet; first means connected to the branch line pressure output and the main line pressure input to selectively provide a branch line pressure output or an inverted branch line pressure output, the outlet of the first means connected to said second and third outlets; second means to selectively block the communication of pressure between the first means and the second outlet; and, third means to selectively block the communication of pressure between the first means and the third outlet.
 12. The pneumatic programming apparatus according to claim 11 wherein the first means includes inverter means having a branch line pressure input, a main line pressure input and an outlet, inverter by-pass means connected in parallel with the inverter means, first valve means to selectively block the branch line pressure input to the inverter means, second valve means to selectively block the outlet of the inverter means, and third valve means to selectively block the inverter by-pass means.
 13. The pneumatic programming apparatus according to claim 12 wherein the second valve means of the first means, the second means and the third means each comprises diaphragm valve means having an inlet, an outlet, and first and second inputs, communication of pressure being allowed between the inlet and outlet when the first input is greater than the second output, and communication of pressure not being allowed between the inlet and the outlet when the second input is greater than the first input.
 14. The pneumatic programming apparatus according to claim 13 further Comprising fourth valve means connected between the main line pressure input and the relay means to selectively block the communication of pressure between the main line pressure input and the relay means.
 15. The pneumatic programming apparatus according to claim 14 wherein the first, third, and fourth valve means each has an inlet, an outlet, and an input.
 16. The pneumatic programming apparatus according to claim 15 further comprising memory circuit means connected to the main line pressure input and having first and second outputs, the first output connected to the first input of the second valve means and the input of the third valve means, and the second output connected to the inputs of the first and fourth valve means and to the first input of the second valve means.
 17. The pneumatic programming apparatus according to claim 16 wherein the second input of the second valve means is connected to the main line pressure input, the second input of the second means is connected to the outlet of the fourth valve means, and the second input of the third means is connected to the outlet of the second means. 